extruded powder, or spherical powder for overbores

A while back I was reading an article on this forum that I think Kirby Allen wrote about suggested powders to use in the overbore cartridges, like the 7RUM. I can't find it now, but it made an impact in my brain, because I shoot a 7rum, and want to get the most barrel life out of it as possible.

If I am correct, the article stated that in order to get the maximum barrel life out of a cartridge like the 7mmRUM then it was suggested to use a very slow spherical powder. I use US869 in mine, and have been since it was new, I have 617 rounds through my barrel now, and I am still very happy with the results, I am getting.

Does it make a difference in throat erosion if you use a spherical powder, vs an extruded powder?

Hello this is my first post, but after hours of reading on the web and speaking with proficient reloaders it sounds like the slowest powder you can use in a given cartridge extends the life of the throat area of your barrel. I have a 300 RUM and asked about this also. This teamed with a sharp shoulder angle with plenty of neck help keeps the hot gases more confined in the neck of the cartridge as opposed to the throat. There was a great article on this about the 6mm CM, which is an improved 243 win. What also comes into play with powder speeds is peak pressures within the barrel with the location of the bullet as it races to exit. This has an affect on throat erosion also. I shoot 4 TMS bullets every 100 rounds to give my throat a touch up and my barrel cannot be any easier to clean. A couple soaked patches of CR-10 followed by some alcohol than kroil.